Search Results

Abstract

OBJECTIVE To evaluate the effect of serum antibody abundance against bovine coronavirus (BCV) on BCV shedding and risk of bovine respiratory disease (BRD) in beef calves from birth through the first 5 weeks in a feedlot.

ANIMALS 890 natural-service crossbred beef calves from 4 research herds.

PROCEDURES Serial blood samples for measurement of serum anti-BCV antibody abundance by an ELISA and nasal swab specimens for detection of BCV and other viral and bacterial BRD pathogens by real-time PCR methods were collected from all calves or subsets of calves at predetermined times from birth through the first 5 weeks after feedlot entry. Test results were compared among herds, over time, and between calves that did and did not develop BRD. The associations of various herd and calf factors with test results were also evaluated.

RESULTS At the calf level, serum anti-BCV antibody abundance was not associated with BCV shedding, but BCV shedding was positively associated with BRD incidence before and after weaning. The mean serum anti-BCV antibody abundance at weaning for a group of calves was inversely related with the subsequent incidence of BRD in that group; however, the serum anti-BCV antibody abundance at weaning for individual calves was not predictive of which calves would develop BRD after feedlot entry.

CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that serum anti-BCV antibody abundance as determined with ELISA were not associated with BCV shedding or risk of BRD in individual beef calves from birth through the first 5 weeks after feedlot entry.

Abstract

OBJECTIVE To compare predictive values, extent of agreement, and gamithromycin susceptibility between bacterial culture results of nasopharyngeal swab (NPS) and bronchoalveolar lavage fluid (BALF) samples obtained from calves with bovine respiratory disease (BRD).

ANIMALS 28 beef calves with clinical BRD.

PROCEDURES Pooled bilateral NPS samples and BALF samples were obtained for bacterial culture from calves immediately before and at various times during the 5 days after gamithromycin (6 mg/kg, SC, once) administration. For each culture-positive sample, up to 12 Mannheimia haemolytica, 6 Pasteurella multocida, and 6 Histophilus somni colonies underwent gamithromycin susceptibility testing. Whole-genome sequencing was performed on all M haemolytica isolates. For paired NPS and BALF samples collected 5 days after gamithromycin administration, the positive and negative predictive values for culture results of NPS samples relative to those of BALF samples and the extent of agreement between the sampling methods were determined.

RESULTS Positive and negative predictive values of NPS samples were 67% and 100% for M haemolytica, 75% and 100% for P multocida, and 100% and 96% for H somni. Extent of agreement between results for NPS and BALF samples was substantial for M haemolytica (κ, 0.71) and H somni (κ, 0.78) and almost perfect for P multocida (κ, 0.81). Gamithromycin susceptibility varied within the same sample and between paired NPS and BALF samples.

CONCLUSIONS AND CLINICAL RELEVANCE Results indicated culture results of NPS and BALF samples from calves with BRD should be interpreted cautiously considering disease prevalence within the population, sample collection relative to antimicrobial administration, and limitations of diagnostic testing methods.

Abstract

Objective—To determine whether a selected set of 20 single nucleotide polymorphism (SNP) markers derived from beef cattle populations can be used to verify sample tracking in a commercial slaughter facility that processes primarily market (ie, culled) dairy cows.

Design—Prospective, blinded validation study.

Animals—165 cows and 3 bulls from 18 states (82% Holstein, 8% other dairy breeds, and 10% beef breeds).

Procedure—Blood was collected by venipuncture from randomly chosen animals just prior to slaughter. The purported corresponding liver samples were collected during beef processing, and genotype profiles were obtained for each sample.

Results—On the basis of SNP allele frequencies in these cattle, the mean probability that 2 randomly selected individuals would possess identical genotypes at all 20 loci was 4.3 × 10^-8. Thus, the chance of a coincidental genotype match between 2 animals was 1 in 23 million. Genotype profiles confirmed appropriate matching for 152 of the 168 (90.5%) purported bloodliver sample pairs and revealed mismatching for 16 (9.5%) pairs. For the 16 mismatched sample pairs, 33% to 76% of the 20 SNP genotypes did not match (mean, 52%). Discordance that could be attributed to genotyping error was estimated to be < 1% on the basis of results for split samples.

Conclusions and Clinical Relevance—Results suggest that this selected set of 20 bovine SNP markers is sufficiently informative to verify accuracy of sample tracking in slaughter plants that process beef or dairy cattle. These or similar SNP markers may facilitate high-throughput, DNA-based, traceback programs designed to detect drug residues in tissues, control of animal diseases, and enhance food safety. (J Am Vet Med Assoc 2005;226:1311–1314)